So I bought a new battery and of course my E30 starts perfectly. I live at the southern end of Black Creek, so I drove up the 400 to Finch and back. It behaved fine all the way except for the following:

The idling revs are not constant at all – always varying. They vary smoothly from 1000 to 2000rpm, up and down up and down a cycle of about 3 to 5 seconds. That's not just slight wavering - that's quite a wide swing right? When I'm at the lights it's as if I'm repeatedly pushing the gas pedal a half-inch and releasing it for no reason. It was doing this from the moment I started it, all thru the drive until I got home.

There were only two times this did not happen: 1) while I was driving at over 2000rpm and 2) the last time I stopped at home. Then it was idling at a constant 1300rpm.

Thoughts welcome!

Bimmer Heaven

12-11-2007, 01:57 AM

Depending on the year, its one of two things; Idle control valve, or idle control module (ETA's)...Some other things can do that too; vacume leaks, etc...

kamus

12-12-2007, 08:51 AM

update: I haven't changed anything yet. But now it doesn't idle at all. Just dies if I release the gas pedal. If I'm careful - I can hold the gas pedal enough to keep it idling, until it warms up. Once warmed up I can release the gas pedal and it idles normally just below 1000rpm.

Does that narrow things down at all? (It's an 87 btw)

T.Dot_E30

12-12-2007, 09:26 AM

When you reconnected the battery did you start it and let it run for a few minutues for it to "learn" the idle?

I suggets removing the connections and letting it sit for a min, re-connect them. Start the car, let it idle for a few minutes, blip the trottle a few times, you'll notice the car will hesitate as the idle drops as the ECU figures it out, after a few times it should smooth itself out.

Happened to me where the car won't idle after connecting the battery, it was bcus i drove the car right after installing it on the highway, when i pulled off the highway, the car wouldn't idle until i removed the connections and let it idle before driving it.

Axxe

12-12-2007, 11:11 AM

Trev, I seam to have the opposite experience. I have to drive the shit out of the car for it learn properly, and then it idles pretty good. But then again, my E30 is ****ed.

T.Dot_E30

12-12-2007, 11:35 AM

Trev, I seam to have the opposite experience. I have to drive the shit out of the car for it learn properly, and then it idles pretty good. But then again, my E30 is ****ed.

Yea i think your right, driving it hard to redline and bringing it back to idle a few times does give it something to adapt to.

I think in my case, i drove it on a highway at a constant rpm for a while, then it wouldn't idle after i got off.

craz azn

12-12-2007, 11:03 PM

Trev, I seam to have the opposite experience. I have to drive the shit out of the car for it learn properly, and then it idles pretty good. But then again, my E30 is ****ed.

+1. Mine did that too when it was stock.

El Gato Liso

12-12-2007, 11:16 PM

im tellin u its the cold weather!

kamus

12-13-2007, 01:00 AM

im tellin u its the cold weather!

You have a point too. I notice a huge difference in the car's behaviour for the first 10 minutes, between being outside overnight, to being inside.

I'll test this further - I'll heat my garage tonight. So in the morning the car should behave as it does in summer! Will report back on my findings..

kamus

12-13-2007, 12:17 PM

Result: The symtoms are much reduced when the garage is warm. The tendency to die disappears sooner - I'm guessing because whatever is cold is taking less time to warm up.